The origins of the the banking Trojan. Kaspersky Lab first detected incidents of a banking Trojan being automatically downloaded on Android devices in August. The cybersecurity company later found this was caused by malicious ads delivered through the AdSense network. The most recent registered attack was on October 19.

Google's AdSense was compromised. AdSense is an ad serving network through which publishers can monetize their sites with targeted text, video, or image advertisements. In this case, it was serving malicious ads on websites that, when displayed on an Android smartphone, would automatically save the Svpeng Trojan onto the device's SD card.

What the Svpeng banking Trojan does. Once downloaded, the Trojan still has to be manually installed to activate. After this happens, Svpeng can steal bank card information by setting up phishing sites, as well as intercept, delete, and send text messages.

The fallout from this attack is not completely clear:

The Trojan was detected on 318,000 computers monitored by Kaspersky over a two-month period, with a peak of 37,000 users attacked on a single day in early October. The attack targeted smartphones with a Russian-language interface, limiting infections to users in Russia and the Commonwealth of Independent States (CIS).

But the full extent of this attack could be even more grave. Kaspersky notes that any site using AdSense could have served up the malicious ads, and AdSense is a popular product. As of November 2016, Google AdSense has a 23% market share of websites in Alexa's top one million ranking, according to Datanyze.

The incident highlights the risk posed by digital ads, which is contributing to a couple of trends:

The threat of malicious ads is a major driver of ad-block adoption. Over 40% of respondents in an Optimal.com survey last year said they use ad blockers out of concern for malware or viruses.

It also encourages signups for paid, but ad-free, subscriptions. The safest way to guarantee against malicious ads is to avoid ads altogether, which could encourage users to buy premium, ad-free subscriptions.

Consumers continue to increase their time spent consuming digital media, while advertisers continue to increase their ad budgets into digital channels.

The influx is not expected to let up in the near future. The US digital advertising industry will continue to experience remarkable growth through 2021 to reach nearly $100 billion in annual revenue, driven primarily by the sustained migration of ad dollars from traditional TV to digital video and the continued increase of social spending.

Overall, the strong growth of the US digital ad market can largely be attributed to increased time spent by consumers on digital media and brands' increased comfort with allocating budgets to digital formats, particularly on digital video. In a recent 2016 survey of almost 400 US ad agencies and marketers, the IAB found that two-thirds of respondents plan on increasing spending on digital video in the next year.

Moreover, mobile will become the top destination for digital ad spending as advertisers continue to attempt to resolve the disconnect between the rapid growth in time spent on phones and tablets and the relatively small share of ad budgets that are allocated to such platforms — known as the mobile opportunity gap. In fact, mobile is set to eclipse desktop ad spend by 2018.

US digital ad revenue is expected to reach nearly $100 billion by 2021, according to BI Intelligence estimates.This represents compound annual growth of 8% from the $68.9 billion expected in 2016.

Mobile is positioned to become the top destination for digital ad spending as advertisers continue to attempt to close the "mobile opportunity gap."

Digital video advertising will grow faster than any other segment over the next five years, as consumers shift time spent online to phones and tablets.Revenue in this category is forecast to rise from $8.5 billion in 2016 to $23 billion in 2021.

Social advertising in all formats is gaining traction and will be among the key drivers of digital ad growth in the next five years.Social ad revenue is poised to climb to $30.8 billionby 2021, up from $15.5 billionthis year.

Artificial intelligence, augmented and virtual reality, and sponsored content will help propel further digital ad growth in the next decade.

In full, the report:

Forecasts US digital ad revenue through 2021.

Highlights the rising popularity of digital media with consumers and brands.

Explores why digital video advertising growth will exceed all other formats over the next five years.

Outlines emerging technologies that will help propel ad growth in the next decade.

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